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Strengthened and toughened SiHfBCN-based hightemperature resistant adhesive with SiC NWs

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Chinese Journal of Aeronautics 2024年第7期37卷 539-549页

作者： Xingang LUAN Xiyue ZHU xichao dong Min LI Laifei CHENG Science and Technology on Thermostructural Composite Materials Laboratory Northwestern Polytechnical UniversityXi’an 710072China

To further improve the performance of binders,a SiHfBCN-based high-temperature resistant adhesive was successfully synthesized by Polymer-Derived Ceramics(PDC)route using TiB2,Polysiloxane(PSO)and short SiC nanowires as *** effect of short SiC nanowires on the adhesive strength at room temperature and high temperature,as well as the reinforcing mechanism was *** with the adhesive without SiC nanowires,after curing(at 170℃)and pyrolysis(at 1000℃)in air,the appropriate adding of SiC nanowires upgrades the room temperature and high temperature(at 1000℃ in air)adhesive strength to(12.50±0.67)MPa(up by about 32%)and(13.11±0.79)MPa(up by about 106%),***,under the synergistic impact of the nanowire bridging,nanowire breaking,nanowire drawing and crack deflection,the optimized adhesive exhibits multi-stage fracture,causing the increscent fracture displacement.

关键词： High-temperature resistant adhesive SiHfBCN SiC NWs Strengthening Toughening

Optimal 3D deformation measuring in inclined geosynchronous orbit SAR differential interferometry

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Science China(Information Sciences) 2017年第6期60卷 33-47页

作者： Cheng HU Yuanhao LI xichao dong Rui WANG Chang CUI School of Information and Electronics Beijing Institute of Technology Key Laboratory of Electronic and Information Technology in Satellite Navigation (Beijing Institute of Technology) Ministry of Education

Three dimensional(3D) deformation can be obtained by using differential interferometric synthetic aperture radar(D-In SAR) technique with the cross-heading tracks data of low earth orbit(LEO) SAR. However,this method has drawbacks of the low temporal sampling rate and the limited area and accuracy for 3D deformation retrieval. To address the aforementioned problems, by virtue of a geosynchronous(GEO) SAR platform,this paper firstly demonstrates the expressions of 3D deformation and the corresponding errors in GEO SAR multi-angle processing. An optimal multi-angle data selection method based on minimizing position dilution of precision(PDOP) is proposed to obtain a good 3D deformation retrieval accuracy. Moreover, neural network is utilized for analyzing the accuracy of the retrieved 3D deformation under different orbit configurations and geo-locations. Finally, the proposed methods and the theoretical analysis are verified by simulation experiments.A 3D deformation retrieval accuracy of the order of centimeter-level or even millimeter-level can be obtained by using the selected optimal multi-angle data.

关键词： geosynchronous synthetic aperture radar(GEO SAR) three dimensional(3D) deformation mea surement multi-angle processing differential SAR(D-InSAR) neural network

Simulation and Analysis of the Impacts of Anisotropic Ionospheric Scintallition on Geosynchronous Synthetic Aperture Radar

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Journal of Beijing Institute of Technology 2017年第1期26卷 115-120页

作者： Yinhui Xu xichao dong Cheng Hu Yuanhao Li School of Information and Electronics Beijing Institute of Technology Beijing 100081 China Beijing Key Laboratory of Embedded Real-time Information Processing Technology Beijing 100081 China

The impacts of ionospheric scintillation on geosynchronous synthetic aperture radar（GEO SAR）focusing is studied based on the multiple phase screen（MPS）*** power spectrum density of electron irregularities is first modified according to the ionospheric *** propagation wave equations in random medium are deduced in the case of oblique incidence in GEO *** amplitude and phase errors induced by the random electron fluctuations are generated by the iterated MPS simulations and are superimposed into the GEO SAR *** the following imaging and evaluation,the effects of the anisotropic ionospheric scintallition on GEO SAR are *** last,the optimized integration time under different ionospheric scintillation conditions are recommended through Monte Carlo *** is concluded that,greater ionospheric fluctuations and longer integration time will result in more severe deterioration,even no focus at all in the worst case.

关键词： anisotropy focusing geosynchronous synthetic aperture radar (GEO SAR) ionospher-ic scintillation multiple phase screen

Feasibility study of inclined geosynchronous SAR focusing using Beidou IGSO signals

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Science China Earth Sciences 2016年第12期59卷 240-242页

作者： xichao dong Cheng HU Weiming TIAN Tian ZHANG Yuanhao LI Beijing Key Laboratory of Embedded Real-time Information Processing Technology Beijing Institute of Technology

Dear editor,Geosynchronous synthetic aperture radar(GEO SAR)[1,2]has an inclined geosynchronous orbit of around 36000 km,which leads to its short revisit time of around 24 hours and a wide coverage of up to approximately one third of the Earth *** long integration time guarantees the fine ***,GEO SAR owns the promising capability of providing images with the high resolution,

关键词：倾斜地球同步轨道 SAR 北斗聚焦信号

Impacts of ionospheric scintillation on geosynchronous SAR focusing: preliminary experiments and analysis

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Science China(Information Sciences) 2015年第10期58卷 191-193页

作者： LI YuanHao HU Cheng dong xichao TIAN WeiMing LONG Teng Beijing Key Laboratory of Embedded Real-time Information Processing Technology Beijing Institute of Technology

Dear editor,Geosynchronous Synthetic Aperture Radar(GEO SAR)has significant potential when applied to hazard and disaster monitoring because of its short revisit time of approximately 24 h and its wide coverage of app... 详细信息

关键词： SAR Impacts of ionospheric scintillation on geosynchronous SAR focusing GEO PSLR Figure preliminary experiments and analysis than

Research progress on geosynchronous synthetic aperture radar

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Fundamental Research 2021年第3期1卷 346-363页

作者： Cheng Hu Zhiyang Chen Yuanhao Li xichao dong Stephen Hobbs The School of Information and Electronics Beijing Institute of TechnologyBeijing 100081China Advanced Technology Research Institute Beijing Institute of TechnologyJinan 250300China The Key Laboratory of Electronic and Information Technology in Satellite Navigation(Beijing Institute of Technology) Ministry of EducationBeijing 100081China Department of Geoscience and Remote Sensing Delft University of Technology2628 Delftthe Netherlands Beijing Institute of Technology Chongqing Innovation Center Chongqing 401120China The School of Aerospace Transport&Manufacturing Cranfield UniversityUK

Based on its ability to obtain two-dimensional(2D)high-resolution images in all-time and all-weather conditions,spaceborne synthetic aperture radar(SAR)has become an important remote sensing technique and the study of such systems has entered a period of vigorous *** imaging modes such as radar interferometry,tomography,and multi-static imaging,have been ***,current in-orbit spaceborne SARs,which all operate in low Earth orbits,have relatively long revisit times ranging from several days to dozens of days,restricting their temporal sampling *** SAR(GEO SAR)is an active research area because it provides significant new capability,especially its much-improved temporal *** paper reviews the research progress of GEO SAR technologies in *** typical orbit schemes are presented,followed by the corresponding key issues,including system design,echo focusing,main disturbance factors,repeat-track interferometry,etc,inherent to these *** analysis and solution research of the above key issues are *** SAR concepts involving multiple platforms are described,including the GEO SAR constellation,GEO-LEO/airborne/unmanned aerial vehicle bistatic SAR,and formation flying GEO SAR(FF-GEO SAR).Due to the high potential of FF-GEO SAR for three-dimensional(3D)deformation retrieval and coherence-based SAR tomography(TomoSAR),we have recently carried out some research related to FF-GEO *** research,which is also discussed in this paper,includes developing a formation design method and an improved TomoSAR processing *** is found that GEO SAR will continue to be an active topic in the aspect of data processing and multi-platform concept in the near future.

关键词： Geosynchronous synthetic aperture radar(GEO SAR) Orbit scheme Disturbance factors Echo focusing Formation flying

时空变背景电离层对GEO TomoSAR成像影响分析

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信号处理 2019年第6期35卷 1018-1024页

作者：张彬董锡超胡程北京理工大学信息与电子学院雷达技术研究所北京100081 卫星导航电子信息技术教育部重点实验室(北京理工大学) 北京100081

地球同步轨道合成孔径雷达层析成像(GEOTomoSAR)是一种将地球同步轨道SAR(GEOSAR)与三维层析成像相结合的技术,它能够克服低轨SAR层析成像中重访时间长、时间去相干严重等缺点,实现对地面场景及时、精确地三维重建。但是由于GEOSAR轨道... 详细信息

地球同步轨道合成孔径雷达层析成像(GEOTomoSAR)是一种将地球同步轨道SAR(GEOSAR)与三维层析成像相结合的技术,它能够克服低轨SAR层析成像中重访时间长、时间去相干严重等缺点,实现对地面场景及时、精确地三维重建。但是由于GEOSAR轨道高,信号能够穿过整个电离层,使得GEOSAR信号时延长,引入严重的相位误差,进而影响GEOTomoSAR三维成像的精度。本文主要从背景电离层对雷达信号传播的影响机理出发,建立了时空变背景电离层影响下的GEOTomoSAR信号模型,进而分析了对三维成像的影响。经过分析,时空变背景电离层对GEOTomoSAR系统的影响主要包括成像目标的相对位置偏移以及高度向成像散焦。最后,通过计算机仿真验证了理论分析的正确性。

关键词：背景电离层时空变地球同步轨道SAR 层析成像

大气层效应对地球同步轨道SAR系统性能影响研究

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雷达学报 2018年第4期7卷 412-424页

作者：胡程董锡超李元昊卫星导航电子信息技术教育部重点实验室(北京理工大学) 北京理工大学信息与电子学院

地球同步轨道合成孔径雷达(GEO SAR)合成孔径时间长、观测范围大,易受到大气层效应时空变化的影响,使成像的聚焦质量和差分干涉处理精度严重下降。该文针对常规对流层和背景电离层等大气层缓变的干扰部分,建立了高精度时频混合GEO SAR... 详细信息

地球同步轨道合成孔径雷达(GEO SAR)合成孔径时间长、观测范围大,易受到大气层效应时空变化的影响,使成像的聚焦质量和差分干涉处理精度严重下降。该文针对常规对流层和背景电离层等大气层缓变的干扰部分,建立了高精度时频混合GEO SAR信号模型,分析了不同大气层参数的时间变化率对成像质量和差分干涉处理精度的影响。针对大气层干扰中对流层湍流和电离层闪烁等随机扰动造成的影响,基于幂律功率谱模型,建立了大气扰动参数和成像质量的定量化分析模型,获得了大气层随机干扰的强度与成像评估指标间的关系。最后,通过仿真验证了模型的有效性,并分析了长孔径时间内缓变和随机扰动的大气层误差对成像和差分干涉处理质量的影响,仿真结果表明:L波段GEO SAR成像和差分干涉处理受时空变电离层干扰的影响十分严重,必须予以补偿;对流层干扰对其影响较小,仅当积累时间达到数百秒时才需要考虑它对成像性能的恶化。

关键词：地球同步轨道合成孔径雷达合成孔径雷达成像对流层干扰影响电离层干扰影响

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气象雷达超低副瓣失配滤波处理技术研究

信号处理 2019年第6期35卷 1051-1056页

作者：鲁俊董锡超胡程北京理工大学信息与电子学院雷达技术研究所北京100081 卫星导航电子信息技术教育部重点实验室(北京理工大学) 北京100081

在雷达信号处理中,通过匹配滤波进行脉冲压缩可以获得最大化的信噪比,有效地减小了雷达回波中噪声对信号的影响。然而,脉冲压缩的输出具有较高的距离旁瓣,在气象雷达探测中,由于空间分布的散射粒子之间反射强度相差较大,弱散射粒子的回... 详细信息

在雷达信号处理中,通过匹配滤波进行脉冲压缩可以获得最大化的信噪比,有效地减小了雷达回波中噪声对信号的影响。然而,脉冲压缩的输出具有较高的距离旁瓣,在气象雷达探测中,由于空间分布的散射粒子之间反射强度相差较大,弱散射粒子的回波容易掩没在强散射粒子的旁瓣中,因此有超低旁瓣的需求。本文主要研究了能够降低旁瓣的非线性调频(NLFM)波形和最小积分旁瓣水平(ISL)失配滤波器,分析了多普勒频移对其性能的影响,并在最小ISL滤波器的基础上通过进一步对滤波器系数加权的方法,使得在回波具有多普勒频移的情况下也能达到超低旁瓣的性能。

关键词：超低旁瓣非线性调频波形失配滤波器多普勒频移